Prominence can be used to define a hierarchy of peaks on an island. To understand this hierarchy, we must first define the basic notion of a prominence parent/child relationship:
Referring to the island illustration, if Peak A is the highest on the island and Peak C is separated from Peak A by its key col, this makes Peak A the parent peak of Peak C. Similarly, the prominence of Peak B is defined by its height above its key col with Peak C. Peak C is therefore the parent peak of B. Since A is the parent of C and C is the parent of B, then A is the grandparent peak of B.
The UK Prominent Peaks replaces the idea of prominence parentage with the concept of ancestors and descendants. Parental links between hills within the same prominence band are set aside. Linkages between a peak and its ancestor in a higher prominence band or its descendant in a lower prominence band become the new focus. Mull, with its 16 Prominent Peaks, provides a good, but manageable-sized example to demonstrate the new relationship of ancestors and descendants.
Compare and contrast the illustrations below and note that the axis on the right is prominence and not height in metres. Following the 1-2-5 Principle, the green band indicates P100 peaks, the yellow band indicates P200 peaks and the red band indicates P500 peaks.
The 1st hierarchy illustration below shows the peaks of Mull with all their parental links. Ben More is the highest point on the island and is the parent for 9 hills, the grandparent for 4 hills and the great-grandparent for 2. The 2nd illustration shows just the links from any hill to its descendants or ancestors in higher or lower bands.
Peaks with parental links
Peaks with links to ancestors and descendants in different prominence bands.
A look at the map shows that there are four ranges of hills on Mull and these correspond to the ancestor-descendant groups defined on the above diagram.
The Ben More family is the largest on Mull whereas Creach Beinn is one of only 15 P500s in the UK with no Prominent Peak descendant. One big advantage of using ancestors and descendants is that these prominence family relationships can then all be contained within the UK Prominent Peak database.
|Dun da Ghaoithe||Dun da Ghaoithe family||P500||H750|
|Ben More, Mull||Ben More family||P500||H750|
|Beinn na Sreine||P200||H500|
|Ben Buie||Ben Buie family||P500||H500|
|Beinn na Croise||P200||H500|
|Creach Beinn||Creach Beinn family||P500||H500|
Splitting the Mull peaks into 4 families, each with a P500 ancestor, is a natural fit with the topography of Mull.